[Rare keratoacanthoma variants].

Keratoacanthomas are made up of the same spinocellular differentiated cell material as squamous cell carcinomas, but they differ from the latter in origin and growth properties. The majority--in our series 98% of 741 examined cases--are of the "crateriform" type, which after rapid growth during the initial stage give way to spontaneous regression, mostly with complete restoration of the cutaneous structure. Less than 2% belong to the rare destructive variants with disturbed or absent regression and persistent invasive growth. Keratoacanthoma marginatum centrifugum, mutilating keratoacanthomas and aggregated keratoacanthomas can lead to extremely severe defects. None of the "conservative" treatment methods recommended in the literature up to now has proved effective, with the exception of surgery and radiotherapy with tumour ratio doses. Many publications are obviously based on uncritically interpreted individual observations.